A company employs two shifts of workers. Each shift produces a type of gasket where the thickness is the critical dimension. The average thickness and the standard deviation of thickness for shift 1, based on a random sample of 37 gaskets, are 9.64 mm and 0.15 mm. The similar figures for shift 2, based on a random sample of 35 gaskets, are 9.66 mm and 0.18 mm. Let12be the mean difference in thickness between shifts 1 and 2.

1. Calculate a 95% confidence interval for12. Round your answers to three decimal places, if necessary.
2. Lower limitUpper limit
3. Based on your answer to parta, are you convinced that the gaskets from shift 2 are, on average, wider than those from shift 1?
4. Select
5. Definitely.
6. Most likely.
7. Probably, not.
8. Definitely, not.
9. Item 3
10. Explain.
11. Because the confidence interval extends from aSelect
12. positive
13. negative
14. Item 4
15. value to aSelect
16. positive
17. negative
18. Item 5
19. value, the population mean difference could beSelect
20. positive
21. negative
22. Item 6
23. .
24. How would your answers to partsaandbchange if the sample sizes were instead 370 and 350?
25. We areSelect
26. definitely
27. most likely
28. probably not
29. definitely not
30. Item 7
31. convinced that the gaskets from shift 2 are, on average, wider than those from shift 1.